Apparatus for determining replenishment of chemicals

ABSTRACT

A method and system for monitoring when chemicals in a development process need replenishing. The system comprises a reference strip bearing a developed graduated scale of exposure of a radiation sensitive medium to a range of exposures and a testing module comprising a radiation shielded pouch and an unexposed radiation sensitive medium within the pouch. The said module include a radiation filter for producing a graduated scale of a range of exposures to radiation on a test strip when it is exposed to radiation and subsequently developed. The scale on the test strip being identical to that on the reference strip when the test strip is exposed to the same radiation, and developed in a developing bath with an acceptable chemical level and composition as that used to produce the scale on the reference strip. Means are provided for comparing the scales on the reference and test strips side-by-side. The test strip and the reference strip each have a datum indicia that align when the test strip and the reference strips are in a datum position relative to each other where the scale on the test strip matches the scale on the reference strip. One or both strips have limits indicia that together define an acceptable range of variation of the graduated scales of the test strip compared with the test graduated scale of the reference strip when the test strip is moved relative to the graduated scale of the reference strip away from said datum position in a direction along the scale of the reference strip to bring a selected first region of the graduated scale of the test strip in alignment with a matching region of the graduated scale of the reference strip.

This invention relates to photographic, x-ray and neutron radiographicfilm processing and is particularly concerned in monitoring when thechemicals used in the development process need replenishing in order toensure uniformity and reliability of the developing process. This ismore of a problem with processing methods where large numbers of x-rayor neutron radiography images are being produced, and the interpretationof crucial features of the images are dependent upon clarity of feint,or obscured, details of the developed image.

As the levels of chemicals of the developing bath are depleted or thecomposition changes, the quality of the resulting images also degradeand there is no reliable way of telling if quality of the image is pooras a result of imperfect development. Therefore important aspects of theimage could be missed when looking at an image that is indistinct due topoor processing.

One way of testing whether the chemicals in the developing bath needsreplenishing is to run a test exposure of a reference image at the startof a development process, for example at the start of a shift orbeginning of a day. However, this would not give any indication of thelevels of chemicals or their composition throughout the day.

An object of the present invention is to provide an easy to useapparatus and method for monitoring the efficacy of an x-ray, neutronradiography or photographic development process.

According to one aspect of the present invention there is provided asystem for monitoring when chemicals in a development process needreplenishing, the system comprising a reference strip bearing adeveloped graduated image of exposure of a radiation sensitive medium toa range of exposures, a testing module comprising a radiation shieldedpouch and an unexposed radiation sensitive medium within the pouch, saidmodule including a radiation filter for producing on the test strip,when it is exposed to radiation and subsequently developed, a graduatedscale of a range of exposures to radiation, said scale on the test stripbeing identical to that on the reference strip when the test strip isexposed to the same radiation as that used tp produce the referencescale and developed in a developing bath with an acceptable chemicallevel and composition as that used to produce the reference scale, meansfor comparing the strips side-by-side, the test strip and the referencestrip each having indicia that align when the test strip and thereference strips are in a datum position where the scale on the teststrip matches the scale on the reference strip, and one or both stripshaving indicia that together define an acceptable range of variation ofthe developed graduated scales of the test strip when the test graduatedscale of the test strip is moved relative to the graduated scale of thereference strip away from said datum position and along the scale of thereference strip so as to bring a first region of the graduated scale ofthe test strip in alignment with a second region of the graduated scaleof the reference strip.

Preferably, the indicia comprises a reference line on each strip thatalign with each other when the strips are in the datum position, and oneor both of the strips have a second line spaced from the first line in adirection measured along the direction that the scales extend thatdefines a limit of acceptable relative displacement of the test stripalong the scale of the reference strip.

The invention will now be described, by way of an example, withreference to the accompanying drawings in which:

FIGS. 1 to 4 illustrate a portable testing kit constructed in accordancewith the present invention, and

FIG. 5 illustrates a second embodiment of the invention.

Referring to FIG. 1, there is shown schematically a light proof pouch 10that contains an undeveloped test control strip 11 of x-ray-film. Thepouch is provided with a radiation filter or mask 12 that defines twobands 13 of varying thickness so that when the strip 11 is exposed tox-radiation, two graded scales of varying grey scales are produced onthe strip when the film is developed. Preferably the band 13 of thefilter has uniform step changes in thickness (and hence density) ratherthan a gradual change in thickness. These step changes are representedin FIG. 1 by the dotted rectangles. The mask 12 is designed so that whenthere is the correct level of chemicals in the developing bath at thecorrect composition, the strip 11 will display two parallel scales 14exhibiting step changes when the film is developed. The test strip 11has a numerical scale of 1 to 21 printed on it (this may be produced bymodifying the mask 12 so that the numerical scale is produced duringexposure of the strip 11 to x-rays). The numbers 1 to 21 correspond toeach step change of density of the mask 12 and are on an arbitraryscale.

The test strip 11 also has indicia comprising two lines marked “S” and“F” at one end of the scale.

An identical reference strip 15 is produced and developed. Like the teststrip 11 the reference strip 15 has two identical scales 16 of gradedgrey levels or contrasts and a numerical scale of 1 to 21. The referencestrip has indicia in the form of a reference line 17 marked at one endof the scales 16. The strip 15 could have two spaced lines S and Fidentical to those on the test strip 11.

In use, the sealed pouch 10 containing the test strip 11 is exposed tox-radiation and the strip 11 is then removed from the pouch in adarkroom or daylight loading box, and processed in the developing bath.The processed strip 11 is then compared with a reference strip 15 bylaying it along side the reference strip.

The reference strip 15 is fixed in place on an illuminated background 9and the test strip is moved axially relative to the reference stripuntil one of the density steps matches one of the density steps of thereference strip. The circles 15(a) show this in FIGS. 3 and 4.

If the reference line 17 on the reference strip 15 corresponds to theletter “S” or is between the lines “S” (Safe) and “F” (Fail) on the teststrip 11, as shown in FIG. 3, then the level of chemicals and thecomposition of the chemicals in the developing bath is acceptable.

If the reference line 17 on the reference strip 15 aligns with the line“F” on the test strip, or is outside the range of “S” to “F” on the teststrip 11, as shown in FIG. 4, then the developing bath chemicals “fail”and must be replenished with fresh chemicals.

In a second embodiment shown in FIG. 5 the test strip 11 is incorporatedin the sealed pouch or cassette 18 of the x-ray film along one edge ofthe film. Either the sealed cassette 18 itself is provided with agraduated radiation filter or mask 19 identical to the filter 12 of FIG.1, or a separate filter 19 is inserted inside the cassette 18 with thefilm prior to exposure. When the x-ray film is exposed to x-rays andsubsequently developed, the developed x-ray image will incorporate itsown test strip 20. This test strip 20 is then compared with a referencestrip 15 in the same way as explained above.

This latter embodiment has the advantage that anyone looking at thex-ray image can see if the developing bath was acceptable at the timethe x-ray was developed. This may make it easier to interpret x-rayimages where the detail is not that good.

It is to be understood that the reference line 17 could be provided onthe test strip and the lines “S” and “F” could be provided on thereference strip 15. In either case, the relative positions of the line17 and the lines “S” and “F” are set so that the reference line 17 fallsbetween “S” and “F” when the chemical levels and composition of thedeveloping bath is acceptable, and falls outside this range when theyare not.

In a further embodiment, the test strip may be used in combination witha liquid crystal display panel of the type that includes a display panelshielded from x-rays and light on which patent's details are displayed.With this type of display the data for the displayed image (for examplepatient's name, date of x-ray, name of consultant, etc.) is entered intothe memory of the device so that the details are displayed on an LCDpanel against a dark background. The displayed LCD image exposes thex-ray film inside the shielding so that when subsequently developed, thefilm displays the patient's details. The present invention may be usedin three ways with such a display system. In the first way, a test strip11 in accordance with FIG. 1 is placed inside a light-proof pouch 10 andlaid alongside the LCD display where it will be exposed to the x-rays(i.e. outside the shielding of the display panel).

In a second way, the LCD display may incorporate a strip of varyingstepped brightness levels corresponding to the step changes of the greyscales in the final developed test strip image so that when the film isexposed and subsequently developed, the test strip 11 of FIG. 1 isproduced on the developed x-ray film.

In a third way, a photographic mask is used inside the x-ray and lightshielded region adjacent the LCD panel to mask part of the unexposedx-ray film. The x-ray film is exposed by exposing the masked film to auniform source of light (which could be generated by the LCD display) soas to produce, in the developed x-ray film, the test strip shown inFIG. 1. This test strip is then compared with the reference strip.

In the above examples the film is an x-ray film. It is to be understoodthat the present invention is applicable to films that have been exposedto light (photographic) or neutrons (neutron radiography).

1-12. (canceled)
 13. A system for monitoring when chemicals in adevelopment process need replenishing, characterised by a referencestrip bearing a developed graduated scale of exposure of a radiationsensitive medium to a range of exposures, a testing module comprising aradiation shielded pouch and an unexposed radiation sensitive mediumwithin the pouch, said module including a radiation filter for producinga graduated scale of a range of exposures to radiation on a test stripwhen it is exposed to radiation and subsequently developed, said scaleon the test strip being identical to that on the reference strip whenthe test strip is exposed to the same radiation and developed in adeveloping bath with an acceptable chemical level and composition, asthat used to produce the scale on the reference strip, means forcomparing the scales on the reference and test strips side-by-side, thetest strip and the reference strip each having a datum indicia thatalign when the test strip and the reference strips are in a datumposition relative to each other where the scale on the test stripmatches the scale on the reference strip, and one or both strips havinglimits indicia that together define an acceptable range of variation ofthe graduated scales of the test strip compared with the test graduatedscale of the reference strip when the test strip is moved relative tothe graduated scale of the reference strip away from said datum positionin a direction along the scale of the reference strip to bring aselected first region of the graduated scale of the test strip inalignment with a matching region of the graduated scale of the referencestrip
 14. A system according to claim 13 wherein the datum indiciacomprises a reference line on each strip that aligns with each otherwhen the strips are in the datum position, and one or both of the stripshave a second line spaced from the first line in a direction measuredalong the direction that the scales extend that defines a limit ofacceptable relative displacement of the test strip along the scale ofthe reference strip.
 15. A system according to claim 13, wherein thepouch is provided with a radiation filter or mask that defines two bandsof varying thickness so that when the strip is exposed to radiation, twograded scales of varying grey scales are produced on the strip when thefilm is developed.
 16. A system according to claim 15, wherein the bandof the filter has uniform step changes in thickness rather than agradual change in thickness.
 17. A system according to claim 13, whereinthe test strip has a numerical scale printed on it corresponding to eachstep change of density of the mask.
 18. A system according to claim 17,wherein the test strip has indicia comprising two lines marked toindicate “safe” and “fail”, respectively, at one end of the scale.
 19. Asystem according to claim 15, wherein the reference strip has identicalindicia and markings to that of the test strip.
 20. A system accordingto claim 13, wherein the pouch is incorporated in a cassette of a filmplate.
 21. A system according to claim 20, wherein the cassette isprovided with a graduated radiation filter or mask that creates thegraduated scale of the test strip on the film.
 22. A method of testingwhen chemicals in a development process need replenishing comprising thesteps of: a) providing a system according to claim 13; b) placing a teststrip in the sealed pouch and exposing the sealed pouch to radiation; c)removing the test strip from the pouch in a darkroom environment andprocessing the test strip in a development bath the composition andcontents of which is to be tested to produce a developed test strip;which is to be tested to produce a developed test strip; d) comparingthe developed test strip with the reference strip by laying the stripsalongside each other; e) moving one strip relative to the other in adirection along the graduated scales until a selected region of thegraduated scales of the test strip matches a selected region of thegraduated scale of the reference strip and thereby establish a matchedposition; f) comparing the position of datum indicia of one of thestrips with the limits indicia of the other strip when the strips are insaid matched position, and g) assessing whether the datum indicia of onestrip is between the limits indicia of the other strip thereby to assesswhether the chemicals in the processing bath need replenishing.
 23. Amethod according to claim 22, wherein the reference strip is fixed inplace on an illuminated background and the test strip is moved axiallyrelative to the reference strip until one of the density steps matchesone of the density steps of the reference strip.
 24. A method accordingto claim 22, wherein the datum indicia is a reference line and thelimits indicia comprise the reference line and a second line.